Plumbing regulations and plumbing codes are very specific about preventing cross connections in a piping system and generally, licensed plumbers are apprehensive of these problems. A `cross connection` is defined in plumbing code books as any actual or potential connection between a potable water system and any source of pollution or contamination.
It is generally accepted that stagnant water should always be considered contaminated and non-potable. Further, it is believed that stagnant water is not only found in marshes and ponds, but is also found in water piping systems and reservoirs that do not have sufficient flow to keep the water active, where water remains still for long period of time for example. Although the fact is often neglected, decaying water in a piping system is in direct contact with potable water and represents a cross-connection contamination that is believed to be harmful to the health of users supplied in water by that piping system.
Generally, municipal water Supply systems are flushed periodically to discharge stagnant water. It is often the case that the discharged water has a foul odour and filthy discolouration. Despite these periodic flushes, it is believed that the stagnation of water in municipal piping systems is a major cause of bad water taste, buildup of sediments in residential hot water reservoirs, and bacterial growth in toilet reservoirs and in drains of bathroom accessories. It is further believed that stagnant water in a piping system is a source of many persistent illnesses, digestive problems and the beginning of many diseases to those using and drinking water from those systems.
Another reason for periodically flushing water supply systems is to eliminate concentrations of chlorine or other disinfectant used in water supply systems which tend to accumulate at regions of low flow. In addition to being detrimental to a good health, high concentrations of chlorine in particular, are known to change the PH value of the water and to deteriorate the protective coating inside water pipes. The material of fabrication of the pipes, which may contain traces of toxic substances are then exposed to the potable water.
The problem of water stagnation is particularly noticeable near water hydrants for example and at the ends of long branches of a piping system where the number of users on a branch pipe is not sufficient for ensuring a proper circulation of water. These situations are often found in newer or partly built subdivisions, and at the end of streets which are supplied in water by oversized pipes. Furthermore, a number of municipalities have water supply systems that were designed according to fire prevention requirements. The size of many branch pipes in these systems is often too large to ensure an adequate circulation of water within the pipe under normal conditions.
The problem of stagnating water in municipal water supply systems has been generally overlooked in the past, and therefore, there are no known system or method for preventing such degradation of water quality.